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Vicariance Dispersal
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Vicariance Model
a once continuous area split into two
a barrier limits movement between areas
(like the breakup of Pangaea)
Dispersal Model
movement of individuals away from an existing population, generally over long distances
dispersal ability depends on the methods & pathways available
Active Dispersal (vagility)
organism moves from one place to another under its own power
Passive Dispersal (pagility)
organism carried by some other physical agent
Corridor
movement along continuous favorable habitat
“easy” for many species
(like the Berring Land Bridge)
Filter (net)
selectively blocks movement of some organisms
organisms must be able to tolerate unfavorable habitat
Sweepstakes
a rare, chance dispersal from one place to another across a major barrier
must survive journey to “new place”
must be able to survive in “new place
Generalities of Islands:
dispersal =
usually sweepstakes
more plants than animals
fewer species in higher trophic levels
lots of endemism
Hawaii
90% of species are endemic
pre-human
habitation
no reptiles
no amphibians
only 1 mammal
mostly birds & flying insects
long-distance dispersal abilities
400 endemic fruit flies
Dwarfism
islands have limited space & resources
more smaller animals can be supported
Gigantism
more resources
less competition & predation
General Evolutionary Trends:
loss of dispersal ability
long distance dispersal a liability
loss of defensive mechanisms
lack of predators
Author
kamrunsreno
ID
12316
Card Set
Vicariance Dispersal
Description
Natural Resources Midterm
Updated
2010-03-29T04:48:40Z
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